October 22, 2007: The U.S. Air
Force has produced an innovative dud with its new SDB (small diameter bomb).
Turns out that while the SDB was being developed, a lot of cheaper competition
showed up. Work began on the 250 pound SDB smart bomb, seven years ago. It was
set to enter service in 2006, and did so. But the only aircraft equipped to
drop it is the F-15E. The SDB was tested in the F-22 (PHOTO), but there are no plans to
deploy F-22s carrying SBD, for several years.
SDB (small diameter bomb) is a
completely new smart bomb design, weighing only 250 pounds. This weapon has a
shape that's more like that of a missile than a bomb (70 inches long, 190
millimeters in diameter), with the guidance system built in. The smaller blast
from the SDB is still pretty substantial (51 pounds of explosives). A new SDB
design has a Focused Lethality Munition (FLM) warhead, which reduces the number
of metal fragments created when the bomb explodes, and increases the blast
effect. This is meant to reduce casualties to nearby civilians. But there are
cheaper solutions to the $50,000 SDB.
Basically, if you add high
precision to a bomb or missile, you increase its cost by $25-50,000. But while
cost is a consideration, it's not the only one. You need just enough explosives
to do the job. Too much bang, and you just endanger your own people. More
important is availability. The infantry need their explosion when they need it,
not when the air force gets around to it. Thus the army prefers to rely on
precision weapons they control. One of the first, widely successful precision
weapons to show up was the fifty pound TOW anti-tank missile. It has a 13 pound
warhead, and, when wars broke out, was mainly used for taking out rooms in
buildings where enemy gunmen were hiding. It was a TOW that got Saddam Husseins
two sons four years ago. Every mech infantry unit has plenty of TOW missiles,
and very few enemy tanks to use them on. So the TOW has become a very popular
precision weapon for the ground troops. Since the 1990s, a more portable ground
combat missile, and just as accurate as TOW, came along in the form of the 26
pound Javelin (PHOTO), with its nine pound warhead. These two missiles are expensive,
with TOW costing $25,000 each, and Javelin $75,000.
For a smaller bang, there's
the AT4 rocket launcher, and its four pound warhead. It's not laser guided, and
you have to be pretty close to use it. But at the normal ranges its used (a
hundred meters or so), it's very accurate, and it's cheap ($2,700). The LAW is
similar, smaller (2.2 pound warhead) and cheaper ($2,000).
Helicopters and UAVs use
Hellfire missiles, which weigh 100 pounds, and have a 20 pound warhead. A
little less than half of a missile warhead is explosives. Hellfire is laser
guided, and good for taking out vehicles full of bad guys, or small buildings.
Hellfire costs $50,000 each. For about the same price you can use the 44 pound
Viper Strike, and its four pound warhead. Even cheaper ($25,000 each), and
smaller, are the new, laser guided 70mm rockets. There weigh 25 pounds and have
a six pound warhead. The Viper Strike is a laser guided glide bomb that
basically comes straight down. The 70mm rocket has a range of about six
The army also has 155mm GPS
guided 155mm shells (Excalibur ) . Each hundred pound shell has about 20 pounds
of explosives (PHOTO). This makes for a bigger bang than Hellfire or Tow, but much less
than smart bombs. There's also a 227mm MLRS GPS rocket (or GMLRS). But this
carries over 150 pounds of explosives. About half the bang of a 500 pound JDAM.
The GPS guided 155mm shell and MLRS rocket each cost over $50,000 each.
The big advantage of these GPS
artillery munitions is that they are available to the troops 24/7, and the need
for fewer rounds per mission means there are fewer problems with running out,
or low, on supplies.
Price is not really a decisive
factor when it comes to these weapons. The whole point of smart (much more
accurate) munitions is to reduce the number of explosions, and to only blow up
what needs to be destroyed. The proliferation of rockets, smart bombs and
missiles, from those with a pound of explosives (LAW) to 500 pound bombs (with
280 pounds), gives troops a lot of flexibility on the battlefield. This makes
American troops much more lethal, and greatly reduces friendly, and civilian,
Although the air force had
smart (GPS guided) bombs since the late 1990s, these came in only two sizes;
half ton and one ton. This proved to be too much blast for urban fighting. The
need for less firepower compelled the air force to quickly modify its GPS
guidance kit to fit on a 500 pound bomb. But that's still 280 pounds of
explosives. The troops wanted precision, and less bang.
In response, the air force
(actually, the navy) developed a 500 pound bomb with all but 30 pounds of the
explosives removed. All these JDAM smart bombs cost less than $30,000 each. But
JDAM requires an air force or navy jet to drop it, and an air force ground
controller to call it in. It's much more convenient to call in army artillery,
for either a GMLRS (if you need a big bang, one that's half as powerful as a
500 pound bomb) or an Excalibur shell (which is less than half the bang of a
SDB). Thus there has not been a huge demand for SDB.